Innovative Materials Driving Noise Control Solutions in Electric Vehicles

As electric vehicle technology matures, the noise masking effect of traditional internal combustion engines is gradually diminishing, presenting electric vehicles with new acoustic challenges. Users’ expectations for interior quietness are also rising, driving the design of automotive acoustic materials and systems toward greater efficiency, lighter weight, and sustainability.

Leveraging its extensive expertise in polymer materials and acoustic engineering, Dow has developed a diverse materials system that explores a closed-loop framework from product design to recycling. To achieve this, Dow has established multiple ISO-standard acoustic laboratories worldwide, utilizing simulation technology to conduct virtual testing and screening of up to 60,000 material combinations.

Additionally, Dow has introduced sustainable strategies such as closed-loop material management, lightweight design, and carbon footprint control to meet regulatory and customer demands, while also providing a replicable low-carbon acoustic materials pathway for other companies in the industry.

With the advancement of electric vehicle technology, the noise from traditional internal combustion engines is fading, leading to new acoustic challenges such as road noise, high-frequency motor noise, and electromagnetic interference. This shift is fundamentally reshaping the design concepts for automotive acoustic materials and systems. In this context, Dow is utilizing its deep knowledge in polymer materials and acoustic engineering to create a diverse materials system that, combined with virtual simulation and testing facilities, promotes the evolution of acoustic solutions toward greater efficiency, lighter weight, and sustainability.

1. Electrification Drives Acoustic System Transformation

The structure of vehicular noise is undergoing a fundamental change. In traditional fuel vehicles, the engine serves as the primary noise source, particularly under acceleration and high load conditions, masking mid to high-frequency noises such as road noise, wind noise, and electromagnetic interference. However, in electric vehicles, the mechanical sound of the power system significantly decreases, making previously masked noise sources more audible. Data indicates that noise from the power system accounts for 50% of total vehicle noise in traditional vehicles, while in electric vehicles, this figure drops to 15%. Consequently, road noise and wind noise from tire-road friction and aerodynamic drag have become dominant.

This change poses challenges to traditional acoustic design strategies, which can no longer rely solely on soundproofing the “engine compartment.” Instead, they must cover more body parts and accurately control noise across different frequency bands. Electromagnetic noise from the electric drive system—such as sound and vibration interference from inverters and high-frequency motors—also presents complex propagation paths and may interfere with onboard electronic systems, demanding higher material shielding performance.

2. User Expectations Rise Alongside System Complexity

Modern electric vehicle consumers’ demand for “quietness” extends beyond merely “reducing noise.” There is now a strong preference for “optimizing sound field experience,” which relates not only to luxury and riding comfort but also directly impacts the accuracy of Advanced Driver Assistance Systems (ADAS) and voice interaction. In scenarios involving assisted or fully autonomous driving, voice prompts, communication among passengers, and even subtle alert signals must be clearly conveyed, necessitating refined noise shielding for specific frequency bands.

As the trend of lightweight electric vehicles strengthens, any added soundproofing materials must minimize weight to avoid affecting driving range. Furthermore, the heightened integration of vehicles and the clear trend toward platform development mean that acoustic system design can no longer be a matter of “adding materials locally” but must become part of a comprehensive system engineering approach.

3. Systematic Acoustic Solutions

Based on its chemicals and materials platform, Dow has established a diverse acoustic materials system that covers multiple frequency bands and adapts to different body structures. Key breakthroughs include:

• Functional Polyurethane Foam (PU Foam): By controlling the pore structure (open/closed cell ratio, pore size distribution) and foam density, the acoustic absorption capabilities for mid to low frequencies can be optimized. High-damping foams used in areas such as dashboards, carpets, and door panels can convert vibrational sound waves into heat, significantly enhancing quietness in the cabin.
• Elastomer Materials (such as EPDM, POE): Used to construct sealing systems and acoustic gaskets, these materials provide sound insulation, waterproofing, and thermal stability, making them suitable for complex areas like doors and chassis.
• Multi-layer Composite Structures: Dow has developed multi-layer material combinations with varying sound impedance to meet specific sound wave reflection/absorption needs. For example, combining sound-absorbing materials with sound-blocking barriers has resulted in optimal attenuation performance in the 400Hz-4000Hz range, effectively addressing wind noise and high-frequency motor whines. This design approach emphasizes not only the sound-absorbing capabilities of the materials themselves but also their coupling characteristics with the vehicle structure, illustrating the evolution from “passive control” to “active tuning.”

Dow has established multiple ISO-standard acoustic laboratories globally, capable of testing acoustic performance at various levels from single materials to complete vehicle components. These tests include, but are not limited to:

• Sound absorption coefficient and sound insulation index tests in semi-anechoic chambers;
• Quantitative analysis of sound transmission and reflection rates in impedance tubes;
• Modeling of material sound-induced vibration responses using excitation systems;
• Measurement of reflection and scattering patterns in reverberation chambers to analyze composite materials’ behavior in complex sound fields.

Combining simulation technology allows for virtual testing and screening of up to 60,000 material combinations, significantly shortening development cycles. The comparison and validation of virtual samples against real samples further enhance the accuracy of modeling tools, providing a reliable database to support subsequent CAE simulation.

4. Sustainable Strategies

Sustainability efforts are primarily reflected in three aspects:

• Closed-loop Material Management: This involves transforming production waste and end-of-life vehicle materials into recycled raw materials through physical/chemical recycling processes. For example, using Dow’s proprietary Dow Binder system, cut scraps can be re-bonded to create new materials, thereby reducing raw material consumption.
• Lightweight Design: The developed sound-absorbing foams are lighter than traditional soundproofing layers, reducing weight by approximately 10-30%, which significantly optimizes overall vehicle mass and energy efficiency.
• Carbon Footprint Control: In material formulations and production processes, priority is given to low-carbon raw materials and green manufacturing methods to comply with the carbon requirements of OEMs in Europe and North America.

This framework not only meets regulatory and customer requirements but also provides a replicable low-carbon acoustic materials pathway for other companies in the supply chain.

Collaboration in research and development has been established with multiple automotive OEMs and tier-one suppliers, who engage in acoustic planning from the vehicle platform design phase and participate in acoustic simulations, platform co-construction, and material selection. Examples include:

• Adding specialized sound-absorbing structures between the battery pack cover and the vehicle floor to control structural noise from the electric drive system;
• Designing sound-absorbing spaces in areas such as the front hood and wheel arches to achieve co-modal control between materials and vehicle structure;
• Participating in acoustic zoning work on electrification platforms like MEB and PPE to ensure targeted material usage.

This “pre-installation development” approach gradually replaces the past passive strategy of “remedying issues after they arise” and represents an inevitable direction for modern automotive acoustic engineering.

Conclusion

The electrification of vehicles has not only reshaped the power systems of automobiles but also introduced unprecedented challenges and opportunities in acoustic engineering. Faced with more complex noise sources and higher comfort requirements, traditional solutions are proving inadequate. Cross-disciplinary collaboration and systematic thinking are becoming essential. The control of low-frequency road noise demands higher material performance and spatial adaptability; managing high-frequency electromagnetic noise requires deep integration with electronic control systems; and under the overarching trend of sustainability, achieving efficient recycling of acoustic materials while balancing costs remains a challenge that the entire industry chain must address together.